<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box {
            width: 200px;
            height: 32px;
            border: 1px solid red;
            background-color: #fff;
            text-align: center;
            line-height: 32px;
            overflow: hidden;
            border-radius: 16px;
        }

        span {
            float: left;
            position: relative;
            width: 140px;
            height: 32px;
            background-color: red;
        }

        span::after {
            position: absolute;
            /* top: 0;
            right: 0; */
            /* width: 0;
            height: 0;
            font-size: 0;
            line-height: 0;      
            border-width: 16px 0 16px 8px;
            border-style: solid;
            border-color: #fff transparent; */

            /* top: 0;
            right: -16px;
            width: 16px;
            height: 32px;
            background-color: red;
            border-radius: 0 16px 16px 0;
            content: ''; */
        }
    </style>
</head>

<body>
    <div class="box"><span>正在加载中</span></div>
    <div class="box2"></div>
</body>

</html>